Field of the Invention
The present application relates to computer graphics and, more particularly, systems, methods, software and devices providing geometry deformation of computer generated animated characters.
Description of the Related Technology
Computer graphic images are created by mathematically modeling the interaction of light with a three dimensional scene from a given viewpoint. This process, called rendering, generates a two-dimensional or three-dimensional stereo image of the scene from the given viewpoint, and is analogous to taking a photograph of a real-world scene. Animated sequences are created by rendering a sequence of images of a scene as the scene is gradually changed over time.
Computer-generated animation of characters is accomplished by manipulating a three-dimensional model of a character into a series of bodily positions, or poses, over a sequence of frames. A character model is often extremely complex, having millions of surface elements and hundreds or thousands of attributes. Due to the complexity involved with animating such complex models, animation tools often rely on armatures and animation variables to define character animation.
A character model is typically constructed from a skeletal representation that is associated with “geometry” that can be visualized as a wire frame mesh associated with the skeletal representation. The skeletal or “stick figure” representation comprises a number of segments or “bones” linked by joints where the position of the bones and joints represent the character's pose, or bodily position. By moving the segments or “bones”, which are the “sticks” of the “stick figure,” the character can be manipulated into a desired pose.
The geometric model comprises multiple model components that represent, for example, layers of bone and tissue that give the character dimension. Model components are associated with the underlying skeletal representation so that the model moves, stretches and deforms as the skeletal segments change position. A character model is completed by applying texture to the surfaces of the geometric model. The textures represent skin, cloth, hair and the like that is visible when the character is rendered. Depending on the artistic goals of the animator, certain features such as hair and cloth may be separately animated (e.g., have their own segmented structure with geometry and texture) rather than simply applied as texture.
Once a model is defined, the animator controls the model's position in each frame of a film either directly or indirectly so as to create a desired visual representation of the character in a film. Although usually only the outer skin of the character is visible in a final video clip, the animator often only manipulates characters with the underlying character model. To achieve a desired artistic result, the computer model of a character is often extremely complex, having millions of surface elements and hundreds or thousands of attributes. Due to the complexity involved with animating such complex models, animation tools often define a subset of control points such as joints in the skeletal model that can be manipulated by the artist. The controlled joint motion is algorithmically translated by animation tools to movements and deformations of the geometric model.